Certain hazardous wastes and wastewater generated by the petroleum industry (K048, K049, K051, F037 and F038) are emulsified mixtures of solids, water, and oil that are extremely difficult to treat, transport, and dispose of. These wastes, in their original state, cannot be directly used as a fuel without considerable dewatering, nor can they be feasibly transported in conventional liquids tankers due to their high solids content. Costs associated with dewatering, transporting, and disposing of these wastes are very burdensome to the petroleum refining and petrochemical industry. Currently, refineries and petrochemical plants are using filter presses, high speed centrifuges, and thermal desorption to process these wastes and waste waters. These currently used processes involve substantial capital investments along with exorbitant operating costs. More importantly, they generate a waste material that is classified as a hazardous waste and must be incinerated and/or land-filled with a significant cost and continued liability. Fiscal costs and future liabilities associated with dewatering, transporting, and disposing of these wastes are very burdensome to the petroleum and petrochemical industries.
The below discussed prior patents define preparation of fibers for use in waste treatment and generally discuss the disadvantages of using absorbent materials in the treatment of waste material due to the dewatering required.
A method of separating kenaf into core and fiber has been described in U.S. Pat. No. 5,970,582. Disclosed is a method and apparatus for separating kenaf into fiber and core uses a modified stick machine conventionally used in the cotton industry for removing trash from unginned cotton. Lengths of kenaf are delivered onto the periphery of a saw cylinder so the toothed wheels snag the fiber and draw the kenaf across a grate. Core is detached from the fiber, passes through the grate and is delivered to a core outlet. Fiber on the toothed wheels are removed by a doffing wheel and delivered to a fiber outlet. Multiple saw cylinder/doffing wheel assemblies are provided.
A typical waste water sludge stabilization process is taught in U.S. Pat. Nos. 4,781,842 and 4,902,431 wherein a sewage sludge is stabilized and converted to fertilizer by mixing the sludge with an alkaline material which is sufficient to raise the pH to at least 12. The mixture is then allowed to dry for at least one day. The alkaline material is selected from cement, kiln dust, and lime dust, to achieve chemical stabilization. Bulking materials, such as slag fines, fly ash, gypsum, etc. may also be added. Such a process is primarily a drying process to eliminate offensive odors and pathogenic microorganisms. The process is not capable of generating a substantial amount of heat to destroy many of the contaminants found therein.
U.S. Pat. No. 6,027,652 describes one process for alleviating the environmental problems associated with the production of oil or chemical sorbent materials is to use a sorbent system based on natural fibers. Over the last several decades, a wide variety of treated natural fibers have been used as sorbents of hazardous materials. These have included tree bark, peat, wood fiber, dealginate kelp, powdered lily, kenaf cores, puffed cereals, and a variety of other cellulosic materials. Each of these fiber types has disadvantages which have prevented them from becoming the material of choice for remediation of oil and chemical spills on land or in water. This patent states that the primary disadvantage of most of these fiber types is that they are naturally hydrophilic and, therefore, tend to sorb large quantities of water. Sorption of water increases the weight of these materials and can seriously decrease their ability to sorb the oil or hazardous chemical which these materials are intended to recover. It is possible to reduce or eliminate the tendency of some of these materials to sorb water by treatment with chemical additives to increase their hydrophobicity.
In U.S. Pat. No. 5,021,390, Hatton teaches a composition for sorbing liquids consisting of various fibrous plant materials treated with the waterproofing agent sodium methyl silicate. In U.S. Pat. No. 5,492,881, Diamond teaches a sorbent system using finely ground cellulose treated with a hydrophobic agent such as paraffin, other waxes, polyvinyl alcohol, hydroxyethyl cellulose or the like. These additives add to the manufacturing expense of the sorbent and may themselves be the source of further harm to the environment.
Another disadvantage, as disclosed in the prior art, of previously disclosed natural fiber based sorbents is that most are generally only capable of sorbing 5–10 times their mass in oil or other chemicals. Additionally, most of these natural fiber compositions have a tendency to sink as they become saturated with oil, water or other chemicals, making recovery of these materials and sorbed chemical from a body of water extremely difficult or impossible.